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Tony Russo, a mosquito and vector control technician with the Marin Sonoma Mosquito Vector Contro

The West Nile virus has claimed its first local victim, and Southern Californians are preparing their defenses against a disease that is spreading alarmingly close to home.

Last week, officials determined that a 57-year-old Orange County man who died last month was a victim of the West Nile virus – making him the first human fatality of the virus in California.

The West Nile virus invasion has expanded westward into California much more quickly than scientists predicted, said Rick Greenwood, director of the Office of Environment, Health and Safety at UCLA.

Carried by birds and spread to humans by mosquitoes, the virus already has killed more than 560 people nationwide since it first appeared in New York in 1999.

Now that it is directly having an impact on Southern California, Los Angeles County health officials are working harder than ever to monitor and contain the disease, which in the most severe cases causes brain infection, fever and death, Greenwood said.

Although the disease is potentially fatal, most people who contract it are not affected adversely by it and would never know they had West Nile virus without a blood test, Greenwood said.

“With West Nile there is a tremendous iceberg below the surface of people who get the disease but don’t get symptoms,” said David Dassey, deputy chief of the Acute Communicable Disease Control Program with the Los Angeles County Department of Health Services.

Dassey said 80 percent of people who contract the disease do not experience any symptoms at all; their bodies fight the virus successfully, develop protective antibodies to it, and are probably immune to future West Nile virus attacks.

The other 20 percent of West Nile virus victims experience symptoms that range from a moderately mild illness characterized by headache, fever, rash, joint pains, and fatigue, to a severe, full-blown fever illness that can result in death, Dassey said.

In these most serious cases, Dassey added, the virus causes meningitis – an infection in the lining of the brain and spinal cord – or even encephalitis – an infection of the brain itself.

“It makes a small number of people seriously ill – perhaps 5 percent,” Dassey said.

Older people are at greater risk for contracting a serious clinical disease from the virus than younger people, Dassey also said. Others at higher risk include those with immune system-suppressing diseases, such as AIDS and diabetes.

Orange County health officials report the man who died last month was using a kidney dialysis bag and lived in a nursing home, which suggests to Dassey that a compromised immune system may have contributed to the severity of the disease for him.

So far, the eastern parts of Los Angeles County have been hit hardest, with the disease usually confined to bird and mosquito populations. No cases have appeared in the coastal areas from Redondo Beach to Malibu, Dassey said.

“Birds are probably dying up there but aren’t being retrieved fast enough” to avoid desiccation by the sun, Dassey said. “You can’t do lab tests on a cooked bird.”

Dassey explains that the virus is primarily a bird disease and that dead birds often signify its arrival to a particular area.

For this reason, the state also employs “sentinel chickens” throughout California to help them monitor the spread of the virus, said Greenwood.

Forty-one human cases of West Nile have been reported across California this year alone, with nine of them occurring in the Los Angeles area, according to the L.A. County Department of Health Services official Web site.

Despite preparations, Dassey said Los Angeles is “fertile ground” for new West Nile infections and predicts that the virus will infect even more people in Los Angeles County next year.

“We have a lot of people here,” Dassey said, “and no one has been exposed to it yet.”

Statistics suggest the virus poses a small threat to those under the age of 65. But the potential danger of the disease and its ability to mutate rapidly are leading Los Angeles public health officials to encourage everyone to avoid contracting it if possible.

There is currently no West Nile vaccine for humans, Dassey said. He notes the low rate of serious infection and the likelihood that people who are exposed to the virus develop their own immunity to it make producing a vaccine not worthwhile.

“When there is a real public health need for it, (scientists) will go out of their way to produce a vaccine, but there is no need for it now,” Dassey said.

Meanwhile, Greenwood said, “The only way to avoid West Nile virus is to avoid mosquito bites.”

He recommends using insect repellents that contain DEET, wearing long-sleeved clothing, and avoiding the outdoors at dawn and dusk when mosquitoes tend to be more active.

Dassey further encourages people to help their neighbors by getting rid of still water on their properties.

“Anything that holds water for three days or more can breed mosquitoes,” Dassey said, including planters, ponds, toys, pools and dog dishes.

“This is one of the few diseases where the general public can help,” Greenwood said.

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